1. Field
The present application relates to methods for firing cordierite bodies and, more particularly, to methods of firing cordierite bodies using reduced firing times.
2. Technical Background
Emission control devices, such as diesel particulate filters (DPF) or honeycomb catalyst carriers, are used to reduce the amount of particulate matter emissions (such as soot for DPFs and NOx and CO for honeycomb catalyst carriers) from diesel engines. DPFs, for example, may capture the particulate matter from the exhaust in the body of the filter. The soot collects in the filter up to a predetermined amount, at which point the filter is regenerated. Such devices may be regenerated (for example by burning) during engine operation to decrease the amount of trapped particulate matter and maintain the collection capacity of the device. Honeycomb catalyst carriers, for example, may support catalytically active components for catalytic converters on automobiles.
Cordierite is commonly used for DPFs and catalysts carriers due to its combination of excellent thermal shock resistance, filtration efficiency, and durability under most operating conditions. The cordierite bodies may be formed from a combination of cordierite precursors and organic constituents in the form of plasticizers, lubricants, binders, pore formers, and solvents.
To form the cordierite bodies, the cordierite precursors and organic constituents are first mixed into a plasticized batch and extruded to form a green ceramic body. Thereafter, the green ceramic body is fired to remove the organic constituents and sinter the cordierite precursors. The firing cycle can be quite long, sometimes greater than about 185 hours in duration, and in some instances, greater than about 200 hours. This is particularly true for larger filters having a diameter of at least about 12 in (about 305 mm).
In addition, during firing, the organic constituents combust, which in the presence of oxygen is a highly exothermic reaction that produces temperature spikes. These temperature spikes can thermally shock and/or crack the cordierite body.
Accordingly, the methods disclosed have been developed in view of these issues, and therefore, an object is to provide alternative firing cycles for producing crack-free cordierite bodies.